The objective is to gain important information about neural mechanisms of control of movement by the globus pallidus. Recent anatomical and physiological data indicate that the globus pallidus represents the final integration center for basal ganglia influences on the limbs and trunk. The basal ganglia have been strongly implicated in the pathogenesis of movement abnormalities associated with Parkinsonism or Huntington's Disease, such as akinesia, rigidity, resting tremor, chorea, athetosis, as well as hemiballismus and a variety of drug-induced dyskinesias. However, the development of a coherent theory of the fundamental disorder in motor control of basal ganglia diseases in humans is limited in part due to an absence of knowledge of the normal physiological role of the basal ganglia in motor and behavioral control. The following SPECIFIC AIMS have been defined: (i) CHRONIC ELECTROPHYSIOLOGICAl STUDIES: Unit activity in the globus pallidus will be recorded, using standard chronic electrophysiological techniques, while monkeys are performing a simple motor response (flexion and extension of the wrist) under different behavioral conditions. These experiments will test the hypothesis that the response of pallidal neurons during arm movement is dependent in part on behavioral contingencies, and not exclusively motor response or sensory stimuli; (ii) ACUTE ELECTROPHYSIOLOGICAL STUDIES: These experiments are designed to provide new information on the integrative functions of neurons in the pallidum and putamen. Since the putamen has been shown by both anatomical and physiological methods to contain somatotopically organized "leg", "arm", and "face" zones, isotopes will be injected in these regions of putamen (defined by mapping corticostriatal evoked focal potentials from precentral gyrus) to determine by autoradiographic methods whether the fibers from these areas terminate in a somatotopic pattern in globus pallidus and substantia nigra. As a separate study, evoked focal potentials will be mapped in the striatum and pallidum to electrical stimulation of the cortical areas of representation of the distal forelimb in primary motor cortex, primary somesthetic cortex, supplementary motor area (SMA), and posterior acute area (PAA) to determine whether inputs from these cortical areas interdigitate or overlap within the putamen. Autoradiographic tracing methods will be used as a control to study the corticostriatal projection in these experiments.